An LCD can display an image by using various methods of controlling light emitted from a backlight unit. For example, an optical compensating film is used for improving color display reproducibility and viewing angle characteristic. The optical compensating film is provided so that the retardation of the film is controlled by stretching a polymer film or coating the film with an organic material to make optical compensation possible in accordance with various demands.
For example, an LCD provided with a liquid crystal panel having a liquid crystal operating mode of a TN mode or an STN mode uses various viewing angle widening techniques to compensate for the narrow viewing angle peculiar to the mode. For example, there are known a method using an alignment dividing means, a half-tone means or the like for averaging pixels while separating the pixels into a plurality of regions having different directions of liquid crystal molecular alignment, a method using a convergent lens or a divergent lens, a method using a viewing angle compensating film, and a method of radically improving the liquid crystal operating mode such as IPS, MVA or OCB. Among these methods, the method of improving the liquid crystal operating mode and the method using a viewing angle compensating film are simpler and have been aggressively put into practice.
Especially, the method using a viewing angle compensating film is simpler than the method of changing and improving the liquid crystal operating mode, because an optical compensating film integrated with a polarizing plate can be stuck to a liquid crystal panel without any change of the liquid crystal panel. That is, this method is a technique by which widening of the viewing angle can be achieved at low cost. A film having oblique discotic liquid crystal inclined or a film having oblique rod-like nematic liquid crystal is known as the viewing angle compensating film. In either case, a liquid crystal polymer is obliquely oriented (e.g. see Patent Document 1). There are also known an obliquely oriented film using a side chain-type liquid crystal polymer (e.g. see Patent Document 2) and a method using an optically oriented film as a nematic polymerizable liquid crystal compound exhibiting homeotropic (perpendicular) orientation to form an obliquely oriented liquid crystal layer (e.g. see Patent Document 3).
However, in the optical compensating film using such an obliquely oriented liquid crystal, optical axes caused by the refractive index anisotropy of the obliquely oriented liquid crystal are formed along the directions of orientation and obliquity of the liquid crystal. There is a problem that the look of an image display device to which the optical compensating film is applied varies according to upper, lower and left and right directions when the image display device is viewed obliquely with respect to the direction of a line normal to its display screen.
Moreover, in the optical compensating film used heretofore and made of a stretched film, an optical axis is decided by vertical stretching in a direction of 0° or horizontal stretching in a direction of 90° with respect to the flowing direction of a long-scale film. Also in the optical compensating film obtained by orientation of liquid crystal, an optical axis is decided by the rubbing or applying direction thereof. For this reason, when the optical compensating film is applied, for example, to a liquid crystal display device, the angle of the optical axis must be designed in accordance with the polarizing plate or the liquid crystal panel. It is however impossible to stick the optical compensating film to the polarizing plate or the liquid crystal panel at a desired angle in the condition that the optical compensating film is a continuous long-scale film. Accordingly, the optical compensating film must be stuck to the polarizing plate or the liquid crystal panel after it is punched into a rectangular shape in accordance with the angle. For this reason, there is apprehension about a problem of contamination with alien matter, breaking, etc. at the time of punching or under shipment and a lowering of production efficiency caused by mistaken sticking.
Patent Document 1: JP 8-5838 A
Patent Document 2: JP 2000-327720 A
Patent Document 3: JP 2002-214610 A